Many of the piezoelectric ceramics, which are used for piezoelectric devices which are utilized for a ultrasonic motor, an inkjet head, and the like, are materials so called PZT, and are oxides including lead (Pb), zirconium (Zr), and titan (Ti). For that reason, from environmental problems, developments of piezoelectric ceramics, which does not contain lead (lead-free piezoelectric ceramics), are being proceeded.
Piezoelectric constant of the lead-free piezoelectric ceramics is low compared to that of PZT, and is not sufficient. For this reason, the lead-free piezoelectric ceramic is subjected to domain engineering, whereby the piezoelectric is improved (S. Wada, Japanese Journal of Applied Physics, Vol. 46, No. 10B, 2007, p. 7039-7043). For the domain engineering described above, there is needed a perovskite-type piezoelectric ceramic, which has a {110} plane orientation in a pseudo-cubic form.
BiFeO3 has an extremely large amount of remanent polarization, and is also high in Curie point. As a result, the perovskite-type piezoelectric material containing BiFeO3 is a promising piezoelectric material. For example, there is exemplified a thin-film piezoelectric material in which BiFeO3 and BaTiO3 are dissolved (Japanese Patent Application Laid-Open No. 2007-287745). However, in the perovskite-type piezoelectric materials containing BiFeO3, there has never been provided a perovskite-type piezoelectric ceramic, which is oriented and is suitable for the domain engineering. The reason resides in that, if a substrate, on which a thin film is to be grown, is appropriately selected, it is easy to attain the orientation in a specific direction, whereas, in a case of a ceramic, because there is not provided a substrate for supporting the orientation, it is difficult to attain the orientation.
For this reason, as a method of aligning a ceramic, there is known a magnetic field orientation (Japanese Patent Application Laid-Open No. 2008-037064). Japanese Patent Application Laid-Open No. 2008-037064 discloses a method involving adding an additive having strong magnetic anisotropy to apply a magnetic field in order to subject the perovskite-type piezoelectric material having small magnetic anisotropy to the orientation by the magnetic field. However, for the orientation by the magnetic field, if an additive having strong magnetic anisotropy is added, the electric characteristics are adversely affected, which is not desirable. Furthermore, the perovskite-type piezoelectric material described in Japanese Patent Application Laid-Open No. 2008-037064 has a {100} plane orientation in the pseudo-cubic form, which is unsuitable orientation for the domain engineering.
The present invention has been made in view of the above-mentioned circumstances, and is aimed to provide a piezoelectric ceramic containing BiFeO3, which is suitable for domain engineering.
Furthermore, the present invention provides a piezoelectric device using the above-mentioned piezoelectric ceramic, and a production method of the piezoelectric device.